Attachment point

ABSTRACT

The attachment point disclosed herein is adapted for applying a substantial load to a fabric sheet. A particularly fitting example of an application for such an attachment point is at the clew of a sail such as a Genoa jib where, in a large sailboat, the jib sheet (a rope) may be holding the sail in position under a load of several hundreds to several thousands of pounds. The attachment point employs a pair of complementary ring members, each having a multiplicity of needle-like teeth. These ring members are clamped on opposite sides of a plurality of cloth layers by means of a metallic inner liner which is rimmed down over the ring members so as to apply a clamping force sufficient to prevent combing of the teeth through the cloth layers under a lateral pressure in the same order of magnitude as the strength of the cloth layers themselves.

United States Patent 3,653,353 Apr. 4, 1972 Davis [54] ATTACHMENT POINT[72] Inventor: Harry T. Davis, West Peabody, Mass.

[73] Assignee: Hood Sailmakers, lnc., Marblehead, Mass.

22 Filed: Sept. 23, 1970 21 1 Appl. No.: 74,773

[52] U.S.Cl ..ll4/l15,24/l4l [51 Int. Cl ..B63h 9/08 [58] FieldofSearch..l14/l14, 115; 24/141,202

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 7,217 1888 GreatBritain ..ll4/ll5 Primary Examiner-Trygve M. Blix Attorney-Kenway,Jenney & Hildreth ABSTRACT The attachment point disclosed herein isadapted for applying a substantial load to a fabric sheet. Aparticularly fitting example of an application for such an attachmentpoint is at the clew of a sail such as a Genoa jib where, in a largesailboat, the jib sheet (a rope) may be holding the sail in positionunder a load of several hundreds to several thousands of pounds. Theattachment point employs a pair of complementary ring members, eachhaving a multiplicity of needle-like teeth. These ring members areclamped on opposite sides of a plurality of cloth layers by means of ametallic inner liner which is rimmed down over the ring members so as toapply a clamping force sufficient to prevent combing of the teeththrough the cloth layers under a lateral pressure in the same order ofmagnitude as the strength of the cloth layers themselves.

2 Claims, 14 Drawing Figures PATENTEDAPR 4 1972 SHEET 1 [IF 3 FIG. I

FIG. 2

FIG. 3

FIG.4

FIG. 5

*1 INV E NTOR l ATTORNEYS PATENTEDAPR 4 I572 3 653 353 SHEET 2 [1F 3INVENTOR ATTORNEYS BACKGROUND OF THE INVENTION This invention relates toan attachment point or grommet, and more particularly, to such anattachment point which is suitable for applying and distributing ratherlarge local loads to a fabric sheet.

In conventional sailmaking procedures, attachment points for heavyloads, e.g., at the clew of a Genoa jib, were provided by hand sewing ina metal or rope ring, together with strips of rope and leather whichwere employed to distribute the load from the ring along the edges ofthe sail away from the clew. In sails where a particularly heavy loadwas to be applied, wire rope might also be used and the load from aprinciple ring might be applied through two or more intermediate ringsso as to facilitate the initial distribution of the concentrated localforces. As the construction of such conventional attachment points istypically performed by hand, the attachment points represented asubstantial item of cost in the sail manufacturing operation.

Among the several objects of the present invention may be noted theprovision of a normal attachment point for applying and distributing asubstantial local load to a fabric sheet; the provision of such anattachment point which does not require a large amount of hand work; theprovision of such an attachment point providing improved load handlingcapability; the provision of such an attachment point which isrelatively lightweight; the provision of such an attachment point whichis relatively simple and inexpensive in construction and which isreliable in use. Other objects and features will be in part apparent andin part pointed out hereinafter.

SUMMARY OF THE INVENTION As noted previously, the attachment point ofthe present invention is adapted for applying and distributing asubstantial or concentrated local load to a fabric sheet such as a sail.A plurality of cloth layers are fastened to the fabric sheet fordistributing the load, the several layers being apertured at the desiredpoint of attachment. A pair of complementary ring members are provided,each of which has on one side a substantially flat face and, on theother side, a toroidally rounded surface. Each ring member also includesa multiplicity of integral needle-like teeth upstanding from therespective flat face. The transverse dimensions of the teeth aresubstantially the same in different directions and are scaled to permitthe teeth to pierce the weave of the cloth layers without substantialdisruption thereof. An inner liner extends through the rings and theaperture in the cloth layers, the liner being rimmed, substantiallysymmetrically, over the rounded surfaces of both ring members, therebyto clamp the multiple cloth layers between the rings under sufficientforce to prevent combing of the teeth through the cloth under lateralpressures of the same order of magnitude as the strength of the clothlayers themselves.

A BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the clew ofa Genoa jib provided with an attachment point constructed in accordancewith the present invention;

FIG. 2 is a sectional view taken substantially on the line 2 2 of FIG.1;

FIG. 3 is a plan view of one of a pair of ring members employed in theattachment point of FIG. 1;

FIG. 4 is a sectional view taken on the line 4-4 of FIG. 3;

FIG. 5 is a plan view of the other of the ring members employed in theFIG. 1 attachment point;

FIGS. 6-9 illustrate seccessive steps in the method of forming theattachment point of FIG. 1;

FIG. 10 is a plan view of a ring member employed in a somewhat differentembodiment of the attachment point of this invention;

FIG. 11 is a sectional view taken substantially on the line 11-11 ofFIG.10;

FIG. 12 is a plan view of another ring member employed in a relativelysmall embodiment of the invention;

FIG. 13 is a sectional view taken substantially on the line 13-13 ofFlG12; and

FIG. 14 is a graph representing the strength of the differentembodiments for various numbers of fabric layers.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2,there is indicated at 11 generally the clew of a Genoa jib. While themain portion of the jib itself will typically comprise only one or twolayers of the sailcloth, depending upon the particular cut used and thesize of the jib, the thickness of the sail is built up toward the clewcorner by successively adding layers of sailcloth on one or both sidesof the main fabric sheet. These several layers are continued fordifferent distances into the body of the sail for distributing the loadand are sewn thereto as indicated at 13 17.

Close to the corner of the clew, the several fabric layers are aperturedand a metal attachment point is applied as may be best seen in FIG. 2. Ajib sheet (rope) is indicated at 19 and is tied to the jib at theattachment point. A shackle might also be used. The attachment pointitself employs a pair of complementary ring members 21 and 23 which areclamped on opposite sides of the cloth layers by means of an inner,generally tubular liner 25 which extends through the rings and theaperture in the cloth layers. One side of each ring member issubstantially flat and includes a multiplicity of integral needle-liketeeth 27 which are driven into the cloth layers. The other side of eachring is rounded, i.e. generally in the form of a toroidal surface. Theliner 25 is rimmed substantially symmetrically over the rounded surfacesof both the ring members, thereby to clamp the multiple cloth layersbetween the ring as is pointed out in greater detail hereinafter.Sufficient force is ap plied in rimming over the liner member so thatthe residual clamping force left on the rings is sufficient to preventcombing of the teeth through the cloth, even when a load approaching thestrength of the cloth layers themselves is applied through the completedattachment point.

The ring 21 is illustrated in greater detail in FIGS. 3 and 4, while thering 23 is illustrated in FIG. 5. Each ring includes threecircumferential rows of teeth. The teeth in successive radially spacedrows are offset so as to substantially reduce the chance of teeth in thesuccessive rows from falling into alignment with the weave of the clothlayers. It may be seen, by comparing FIGS. 3 and 5, that the pins in thering 21 form a sort of right-hand spiral when viewing the flat facewhile the teeth on the ring 23 form a left-hand spiral when similarlyviewed. Accordingly, it may be seen that the spirals will effectivelyinterleave when the two rings are clamped on opposite sides of theplural cloth layers.

Preferably, the teeth 25 are cast integrally with the rings 21 and 23,using conventional investment casting procedures. The preferred materialis 316 stainless steel. After casting, the rings are thenelectro-polished to provide a bright finish and to further reduce thepossibility of corrosion.

As may be seen from FIG. 4, the teeth 27 are generally needle-like incharacter so that they can pierce the weave of the various cloth layerswithout substantial disruption thereof. In other words, the transversedimensions of the teeth are substantially the same in differentdirections at any given level or height. While a circular cross sectionis preferred, this shape is not necessary as long as the transversedimensions are sufficiently equal so that the teeth are not flat orblade-like. As will be understood, a flat or blade-like shape would tendto disrupt or cut the weave, disturbing its integral nature.

While the side of the ring member carrying the piece 27 is generallyflat, it has been found desirable to round the corner at the outside ofthe ring so as to prevent cutting of the cloth layers by the outer edgesof the rings. Similarly, while the outer surfaces are generally of atoroidally rounded shape, a slight shoulder may be provided as indicatedat 33 to facilitate locking of the rimmed-over portion of the liner 25.

The method of applying this attachment point is illustrated in FIGS. 6through 9. The plural cloth layers are first die-cut to provide acircular aperture 35 in the several cloth layers as illustrated in FIG.6. A tubular sleeve 37 (which later becomes the liner 25) is insertedthrough the aperture (FIG. 7) and the rings 21 and 23, centered on thesleeve, are pressed against the cloth layers on opposite sides thereofso as to drive the 'teeth 27 into the weave of the cloth layers. As afurther precaution against rusting, the toothed sides of the rings 21and 23 may be sprayedwith an acrylic spray coating prior to beingpressed into the cloth layers. The sleeve 37 is preferably alsoconstructed of electropolished 316 stainless steel and is annealed so asto permit working during the subsequent rimming operation.

After the rings have been positioned, the sleeve 35 is then rimmed over,substantially symmetrically, by a pair of dies 38 and 39 as illustratedin FIG. 8. The ends of the sleeve are preferably slightly beveled tofacilitate initial entry of the dies. A final closing or rimming ispreferably provided by a separate set of dies at 41 and 42 asillustrated in FIG. 9. As noted previously, relatively heavy pressuresare provided during the rimming operation so that the residual clampingforce on the ring members 21 and 23 is sufficient to prevent combing ofthe teeth through the cloth layers under lateral forces which are in thesame order of magnitude as the ultimate strength of the cloth layersthemselves.

In one particular construction of the embodiment illustrated in FIGS. 29, the outer diameter of the rings 21 and 23 was 2.688 inches and theinside diameter was 1.688 inches; the outer diameter of the sleeve 35which became the liner was 1.625 inches and its wall thickness was 0.125inches; the dies 38 and 39 and the dies 41 and 42 were applied with aforce which reached a peak pressure of 30 tons. The residual clampingpressure, though not subject to exact measurement, was then sufficientto prevent combing of the teeth 27 through the weave of the cloth duringtests to failure.

In general, it is believed that the teeth provide interlocking of therings with the woven fabric and that the relatively high clampingpressure so compresses the mass of fibers that combing of the teeththrough the weave is substantially prevented. The mode of ultimatefailure is then such that, around most of the circumference of theaperture, pieces of woven cloth are torn intact from the several layers.In a small downstream area, some of the cloth may be entirely removedfrom between the rings, but typically the teeth are bent over ratherthan being combed through the cloth. With 12 layers of 8 oz. cloth,attachment points constructed as just described will typically withstandan applied force of well over 6,000 pounds. While this may not be fullyequal to the ultimate strength of a strap of individual cloth layers ofwidth equal to the diameter of the aperture, it is generally within anorder of magnitude. It can thus be seen that a very strong attachmentpoint is provided. Accordingly, this attachment point is suited for usein situations where a substantial local load has to be applied to alarge fabric sheet. For example, such an attachment point may be used atthe clew of a Genoa jib suited for a relatively large sailing craft,e.g. the 12 meter yachts raced in international competition.

While it is difficult to designate a corresponding conven tionalconstruction for comparison, it may in general be noted that thisembodiment will typically provide greater strength with about half theweight than the most directly comparable conventional construction.

The ring employed in another embodiment is illustrated in FIGS. and 11.This ring, designated 51, employs two rows of teeth 53, which, thoughgenerally conical in nature, are still essentially needle-like. Theteeth are arranged in two rows with the teeth being staggered betweenthe two rows. Since only two rows are employed, the rings used on bothsides of the cloth layers may be of the same construction, and it is notnecessary to provide both left-hand and right-hand members of differingconstruction. This arrangement is generally suitable for intermediateloads. Further, with the use of a relative thin liner member, theover-all thickness of the attachment point may be kept small enough sothat essentially conventional hooks and snap fixtures may be usedherewith.

FIGS. 12 and 13 illustrate the ring used in a still smaller version ofthe attachment point. In this version, only a single row of teeth 57 areused, the ring 55 being correspondingly narrower so that a very lightand easily managed attachment point is provided.

FIG. 14 is a graph representing the variation in strength with thenumber of layers of cloth for the several illustrated embodiments of theinvention. In each of these embodiments,- the cloth layers are wovendaeron 8 oz. sailcloth having a strength of about 300-400 pounds perinch. As there will understandably be some statistical variation fromsample to sample, the performance of the various embodiments has notbeen designated as a single line but rather by a corresponding area, thearea being intended to include approximately percent of the statisticalpopulation of test samples.

The shaded area designated A represents the general range of strengthprovided by the larger size attachment point of FIGS. 2 through 9 withdifferent numbers of cloth layers. Similarly, the shaded area designatedB represents the behavior of the embodiment illustrated in FIGS. 10 and11, while the area designated C correspondingly represents theembodiment of FIGS. 12 and 13. In the first two, the liner sleeve usedhad an initial wall thickness of 0.125 inches and forces ofapproximately 30 tons were applied during rimming of the sleeve. In thethird (FIG. 13), a thinner liner was used having an initial wallthickness of 0.065 inches and the rimming force was held to 20 tons toprevent cutting of the fabric. The thinner liner may also be used withthe intermediate size rings since, as noted previously, it may bedesirable in some situations to use a thinner liner so as to provide anattachment point which is useable with relatively small hooks and snapfasteners. With the intermediate rings, the thinner liner, that is, onehaving an initial wall thickness of 0.065 inches, may be used withoutsignificantly weakening the strength of the attachment point.

In view of the foregoing, it may be seen that several objects of thepresent invention are achieved and other advantageous results have beenattained.

As various changes could be made in the above construction and methodswithout departing from the scope of the invention, it should beunderstood that all matter contained in the above description or shownin the accompanying drawings shall be interpreted as illustrative andnot in a limiting sense.

I claim:

1. In a sail, an attachment point for applying and distributing asubstantial local load to the sail, said attachment point comprising:

a plurality of cloth layers sewn to the sail for distributing said load,said layers being apertured at the desired point of attachment;

a pair of complementary ring members investment cast of stainless steel,each of which has on one side a substantially flat face and on the otherside a substantially toroidally rounded surface, each ring memberincluding also a multiplicity of integral needle-like teeth of roundcross section upstanding from the respective flat face, said teeth beingadapted to pierce the weave of said cloth layers without substantialdisruption thereof;

a stainless steel, generally tubular liner extending through one of saidring members, the aperture in said cloth layers and the other of saidring members, said liner being rimmed substantially symmetrically overthe rounded surfaces of both of said ring members thereby to clamp saidmultiple cloth layers between said rings under sufficient force tosubstantially prevent combing of said teeth through the cloth under alateral pressure in the same order of magnitude as the strength of saidcloth layers.

2. An attachment point as set forth in claim 1 wherein said liner isrimmed over under a force in the order of 30 tons.

1. In a sail, an attachment point for applying and distributing asubstantial local load to the sail, said attachment point comprising: aplurality of cloth layers sewn to the sail for distributing said load,said layers being apertured at the desired point of attachment; a pairof complementary ring members investment cast of stainless steel, eachof which has on one side a substantially flat face and on the other sidea substantially toroidally rounded surface, each ring member includingalso a multiplicity of integral needle-like teeth of round cross sectionupstanding from the respective flat face, said teeth being adapted topierce the weave of said cloth layers without substantial disruptionthereof; a stainless steel, generally tubular liner extending throughone of said ring members, the aperture in said cloth layers and theother of said ring members, said liner being rimmed substantiallysymmetrically over the rounded surfaces of both of said ring membersthereby to clamp said multiple cloth layers between said rings undersufficient force to substantially prevent combing of said teeth throughthe cloth under a lateral pressure in the same order of magnitude as thestrength of said cloth layers.
 2. An attachment point as set forth inclaim 1 wherein said liner is rimmed over under a force in the order of30 tons.